Gross weight (GW) and center-of-gravity (CG) of an aircraft, such as a rotorcraft, impact the static and dynamic characteristics of flight. Accurate, in-flight estimation of the GW and CG can substantially improve performance. For example, knowledge or feedback of GW and CG can be used within a condition-based maintenance system, a health-and-usage management system, automatic flight controls, and mission planning systems.
Conventional techniques for estimating GW/CG include: (1) aircrew estimates, supplemented by correction for fuel weight using integrated fuel flow, (2) measurements of on-ground strain on landing gears, and (3) estimation of GW/CG from other measured aircraft state parameters. Practically, it is not feasible to rely on aircrew estimates for most applications. It is difficult to properly temperature-compensate measurements of landing gear strain. Estimate of GW/CG from other measured state parameters is difficult because GW/CG represent independent degrees of freedom for an aircraft. Moreover, measuring aircraft GW/CG in a hangar is time-consuming and merely serves as a crude estimate because GW/CG may change (e.g., due to fueling/de-fueling).